A dental filling is a common procedure used to restore a tooth damaged by decay or trauma. The process involves removing the damaged section and filling the space with materials like composite resin or amalgam to seal the area from bacteria. Although the procedure is routine, the restoration can sometimes fail due to procedural errors or material limitations. Understanding the signs and reasons behind a failed filling helps patients seek timely correction.
Signs of a Problematic Filling
One immediate sign of a problem is prolonged sensitivity to temperature changes, such as when drinking hot or cold liquids. While temporary sensitivity is expected after a procedure, persistence beyond a few weeks may indicate the filling is not properly sealed.
Pain felt specifically when biting down or chewing is another common symptom. This often suggests the filling material is too thick, interfering with the natural alignment of the upper and lower teeth. The filling may feel “high” or prominent, creating an uneven pressure point that irritates the tooth’s nerve.
Visually, a faulty filling might show obvious signs like a chip, a crack, or material breaking away from the tooth. Discoloration or a dark shadow around the edges can signal new decay developing underneath the restoration.
A rough edge or a noticeable gap where the tooth and filling meet is a physical indication of failure. Floss that repeatedly shreds or catches near the filling suggests a marginal overhang or open margin. These physical defects compromise the seal and allow bacteria and food particles to enter the vulnerable area.
Technical Reasons Why Fillings Fail
Fillings often fail due to technical issues during placement, particularly those involving the adhesive properties of composite resin materials.
Moisture Contamination and Curing Errors
One frequent cause is moisture contamination, where saliva or blood contacts the prepared tooth surface before the bonding agent is applied. The presence of moisture significantly weakens the bond strength, preventing the resin from achieving a durable seal. Another procedural error relates to the curing process, where the composite resin is hardened using a blue light. Improper curing, such as insufficient light exposure or poor positioning, results in an inadequately polymerized material. This leaves the filling softer than intended, increasing the risk of premature wear and fracture.
Incomplete Decay Removal
Failure to remove all existing decay before placing the new material leads to recurrent or secondary decay. This decay undermines the filling from the inside, weakening the surrounding tooth structure. Even if the filling material was perfectly placed, the restoration will eventually fail as the underlying decay progresses.
Shaping and Shrinkage Issues
If the dentist does not properly contour or shape the filling, it can lead to occlusal trauma, causing persistent pain. Another element is polymerization shrinkage, where the resin material slightly contracts as it cures, creating a microscopic gap at the margin. This marginal leakage allows bacteria to penetrate beneath the filling, leading to sensitivity and secondary decay over time. Larger restorations are more susceptible to this shrinkage effect.
Steps to Correct a Faulty Filling
If signs of a faulty filling appear, contact the dental office immediately for an assessment. The dentist will use visual inspection and X-rays to determine the nature and extent of the failure, checking specifically for decay beneath the restoration.
For minor issues like a “high bite,” correction may be a simple adjustment where the dentist uses a fine bur to reshape and polish the filling surface. More significant failures, such as a compromised seal or recurrent decay, typically require the complete removal of the old filling and replacement with a new restoration.
The dentist must ensure all decay is eradicated and use meticulous isolation techniques to prevent moisture contamination during the re-bonding process. If decay has advanced significantly, reaching the pulp chamber, the tooth may require a root canal procedure to save it from extraction. If the remaining tooth structure is too weakened to support a new filling, a full-coverage crown might be recommended to protect the tooth from fracture. Addressing a faulty filling promptly prevents more serious complications.